Electrical submersible pumps (ESP) are commonly used in wells for hydrocarbon fluid production. An ESP is made up of a number of modules brought to the well site. These modules include a pump, a motor, and a seal section or pressure equalizer. The modules may also include a gas separator. Additionally, the pump and motor may comprise tandem units that are connected at the well site. The connections between the various modules are often smaller in diameter than the remaining portions of the modules. These connections may be bolted flanges or they may comprise threaded collars. When installing the ESP, a motor lead and possibly other lines, are attached by banding alongside portions of the ESP.
It is important to keep the motor lead and the other lines in a straight line parallel to the axis of the ESP. If the motor lead and other lines curve helically around the ESP, a chance exists that the ESP could become stuck while lowering the ESP into the well. Because of the length of the ESP, a lower portion of the motor lead and other lines may not be visible while banding upper portions of the motor lead and lines to the ESP. Maintaining the motor lead and accessory lines straight can be difficult.
Also, the connections between the various modules normally result in an area of reduced diameter along the ESP. As well fluid flows upward past the motor to the pump intake, it will encounter at least one the reduced diameter area above the motor before reaching the pump intake. Turbulence may result, which may cause wear and erosion of the housings at the reduced diameter area.
The threaded collar type of connection between modules employs an internally threaded collar that fits around a neck of one of the modules. The collar has an axial width that is less than the length of the neck so that the motor shafts within the adjoining modules can be stabbed together before the collar is made up. A risk exists that the collar will loosen and drop down to the base of the neck due to vibration of the ESP during operation. If so, the modules would become disconnected from each other.